Fix documentation for rollback() (#647)
Fix documentation for rollback() (#647)

The expected rollback ID is an integer.
Juniper/py-junos-eznc,spidercensus/py-junos-eznc,pklimai/py-junos-eznc,spidercensus/py-junos-eznc,Juniper/py-junos-eznc,pklimai/py-junos-eznc,pklimai/py-junos-eznc,Juniper/py-junos-eznc,spidercensus/py-junos-eznc